How do I convert materials from Blender Internal to Cycles?
The Python script at https://blenderartists.org/forum/showthread.php?394600-Materials-Specials-amp-conversion will automatically convert all of your materials and textures over so that they are compatible with Cycles.

The script tries to make the Cycles materials look as much like the Blender-Internal materials as possible, but I imagine you'll still need some tweaking, because of the inherent differences between the two render engines.